1. Field of the Invention
The present invention relates to a pneumatic radial tire that has the sidewall thickness reduced in order to achieve tire weight reduction.
2. Description of Prior Art
One of the major objectives in the current tire technology is to reduce the tire weight and, hence, fuel consumption. To this end, various proposals have been made and one of them is to reduce the rubber thickness of the sidewalls.
A common practice adopted by conventional tires to make them lighter and increase fuel efficiency is to reduce the rubber thickness of sidewalls to values between 2.0 and 3.0 mm.
A mechanism by which the sidewalls of a tire are damaged is illustrated in FIGS. 5 to 7. Suppose that a tire A mounted on a rim B is rotating along a curb D (usually 170 mm high) in such a way that the outer lateral edge of a rim flange C nearly touches the curb D. Since a sidewall A1 of the tire A protrudes outward of the outer lateral edge of the rim flange C, the sidewall A1 is forced between the end edge of the curb D and the outer lateral edge of the rim flange C (see FIG. 7), occasionally causing damage to the outer lateral surface of the rubber layer in the sidewall A1.
However, with the above-described structure of conventional tires, in which the rubber thickness from the outer lateral surface of each sidewall to the carcass layer is somewhere between 2.0 and 3.0 mm, there is little likelihood that a bruise in the rubber layer in sidewall A1 will propagate to the carcass embedded in that sidewall.